Brushless direct current motor, compressor and air conditioner having the same

ABSTRACT

A brushless direct current motor, includes a rotor which comprises a permanent magnet, a stator which comprises coils associated with a plurality of phases which form an electrical field for generating a torque by interaction with a magnetic field which is generated by the permanent magnet, and a load prevention part which is disposed inside the stator to electrically connect and disconnect the coils of the plurality of phases according to a temperature variation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2007-0014524, filed on Feb. 12, 2007 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

A brushless direct current motor, a compressor and an air conditionerhaving the same consistent with the present general inventive conceptrelate to improving a configuration preventing an overload of abrushless direct current motor.

2. Description of the Related Art

In general, an air conditioner acting as a heat pump operates in aheating mode and a cooling mode according to a demand of a user. Forexample, the heat pump heats a room in the heating mode in winter, andcools the room in the cooling mode in summer. Also, the heat pump mayadjust the humidity of the room, and clean the air of the room.

In general, the heat pump includes an indoor unit including an indoorheat exchanger to heat or cool a room and an indoor fan, and an outdoorunit including an outdoor heat exchanger, an outdoor fan and acompressor.

During a heating cycle in the heating mode, at first, the compressorcompresses a refrigerant. The compressed refrigerant is supplied to theindoor heat exchanger, and air which is heated by the indoor heatexchanger is discharged into the room, thereby heating the room.

In a cooling cycle of the cooling mode, at first, the compressorcompresses the refrigerant. The compressed refrigerant is supplied tothe outdoor heat exchanger and evaporated in the indoor heat exchanger,and air which is cooled by the indoor heat exchanger is discharged intothe room, thereby cooling the room. The refrigerant subject to theheat-exchange operation in the indoor unit is supplied to the outdoorheat exchanger.

In the cooling and heating processes, the compressor repeats acompressing process of the refrigerant. The air conditioner successivelyperforms compression, condensation, expansion and evaporation processes.

In general, a compressor includes a driving shaft rotated by a magneticflux variation of a brushless direct current motor provided with astator and a rotor having a permanent magnet, and a rolling pistoncoupled to an eccentric part of the driving shaft to rotate in an innerspace of a cylinder as the driving shaft rotates.

Also, the compressor includes a control part to control an operation ofthe brushless direct current motor based on various sensors to achieve astable and safe operation. The sensors may sense the position of therotor, or include a thermostat which senses temperature. However, thebrushless direct current motor may be required to be used under poorenvironmental conditions, which may be problematic for the sensors.

Accordingly, if the stator is provided with a temperature sensor and thebrushless direct current motor is used under poor environmentalconditions, the temperature of the environment in which the brushlessdirect current motor is used may improperly influence the temperaturesensor.

SUMMARY OF THE INVENTION

The present general inventive concept provides a brushless directcurrent motor, a compressor and an air conditioner having the sameoperable within various environments.

The present general inventive concept also provides a brushless directcurrent motor, a compressor and an air conditioner having the same witha simple configuration more accurately responsive to the temperature ofthe motor of the environment in which it is used, thereby improvingreliability.

Additional aspects and utilities of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the present general inventive concept.

The foregoing and/or other aspects and utilities of the present generalinventive concept can be achieved by providing a brushless directcurrent motor, including a rotor which includes a permanent magnet, astator which includes a coil of a plurality of phases which forms anelectrical field to generate a torque by interaction with a magneticfield which is generated by the permanent magnet, and a load preventionpart which is disposed inside the stator to electrically connect anddisconnect the coil of the plurality of phases according to atemperature variation.

The load prevention part may be disposed to an area in which the coil ofthe plurality of phases crosses each other.

The load prevention part may include a casing which is coupled to thestator to be connected with the coil, a moveable member which isdisposed to the casing to connect each phase of the coil of theplurality of phases, and a transformable member which is coupled to thecasing to move between a connected position in which the moveable memberis connected with the coil, and a disconnected position in which themoveable member is disconnected from the coil.

The transformable member may include a bimetal.

The load prevention part further may include an elastic member whichelastically presses the moveable member toward the transformable member.

The foregoing and/or other aspects and utilities of the present generalinventive concept can be achieved by providing a compressor, including abrushless direct current motor which includes a rotor which includes apermanent magnet, a stator which includes a coil of a plurality ofphases which forms an electrical field for generating a torque byinteraction with a magnetic field which is generated by the permanentmagnet, and a load prevention part which is disposed inside the statorto electrically connect and disconnect the coil of the plurality ofphases according to a temperature variation, and a cylinder whichcompresses a refrigerant by rotation of the brushless direct currentmotor.

The load prevention part may be disposed to an area in which the coil ofthe plurality of phases crosses each other.

The load prevention part may include a casing which is coupled to thestator to be connected with the coil, a moveable member which isdisposed to an inner side of the casing to connect each phase of thecoil of the plurality of phases, and a transformable member which iscoupled to the casing to be transformed according to a temperaturevariation to move the moveable member.

The load prevention part further may include an elastic member whichelastically presses the moveable member toward the transformable member.

The compressor may further include a control part which controls thebrushless direct current motor not to operate if the transformablemember is transformed to separate the moveable member from the coil.

The foregoing and/or other aspects and utilities of the present generalinventive concept can also be achieved by providing an air conditioner,including a compressor which compresses a refrigerant, a heat exchangerwhich evaporates the refrigerant which is compressed by the compressor,and a fan which forms a flow to allow heat exchange with the heatexchanger.

The foregoing and/or other aspects and utilities of the present generalinventive concept can also be achieved by providing a brushless directcurrent motor comprising a rotor, a stator including a coil, a moveableconductor, to establish a current path with the coil when at a firstposition and to cause a short in the current path when at a secondposition.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and utilities of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the exemplary embodiments, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of an air conditioner according to anexemplary embodiment;

FIG. 2 schematically illustrates a configuration of an outdoor controlpart in FIG. 1;

FIG. 3 is a sectional view of a compressor in FIG. 1;

FIG. 4 is a spread view of a stator in FIG. 3;

FIG. 5A is an enlarged sectional view of a load prevention part;

FIG. 5B is a perspective view of a moveable member in FIG. 5A; and

FIGS. 6A to 6C are a sectional view and circuit connecting diagramsillustrating an operating state of the load prevention part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to likeelements throughout. The exemplary embodiments are described below so asto explain the present general inventive concept by referring to thefigures.

An air conditioner according to the present general inventive conceptmay be applied to a ceiling type conditioner, a window mounting typeconditioner, a floor standing type conditioner, etc. As used herein, anair conditioner includes both an air conditioner used as a heat pump forheating and cooling, and an air conditioner used only for cooling.Hereinafter, an air conditioner including an indoor unit and an outdoorunit will be described as an exemplary embodiment of the present generalinventive concept. The air conditioner in this example is used as a heatpump.

As illustrated in FIGS. 1 to 5B, an air conditioner 100 according to anexemplary embodiment of the present general inventive concept includesan outdoor unit 120 including a compressor 210, an outdoor heatexchanger 121, and an outdoor fan 123. The air conditioner 100 mayfurther include an indoor unit 110.

The indoor unit 110 is disposed in a room such as an office to cool orheat air of the room. The indoor unit 110 includes an indoor heatexchanger 111 which a refrigerant compressed by the compressor 210circulates, and an indoor fan 113 to circulate an indoor air to beheat-exchanged with the indoor heat exchanger 111. The indoor unit 110includes an indoor control part (not shown) to control driving of theindoor fan 113 depending on an input information inputted by a user.

The outdoor unit 120 includes the compressor 210, the outdoor fan 123and the outdoor heat exchanger 121. The outdoor unit 120 includes anoutdoor control part 125 electrically connected with the indoor unit 110by wireless or wired connections to control the compressor 210, theoutdoor fan 123, etc. The outdoor fan 123 is disposed to be adjacent tothe outdoor heat exchanger 121, and circulates an outdoor air toexchange heat with the outdoor heat exchanger 121.

The outdoor heat exchanger 121 is disposed on an air flow path of theoutdoor fan 123 to exchange heat with the outdoor air.

In this example, compressor 210 includes a brushless direct currentmotor 230, a cylinder 217, a housing 211, a driving shaft 213, a rollingpiston 219, a control part 270, and a sensor part 280. The compressor210 may further include an accumulator (not shown) including a gasliquid separating pipe (not shown). The compressor 210 may furtherinclude a rectifier 291, and an inverter part 293.

The housing 211 forms an external appearance of the compressor 210. Thehousing 211 includes a lower casing (not shown) and an upper casing (notshown), and accommodates various components therein.

The driving shaft 213 has an elongated bar shape, and transmits arotation force of a rotor 231 to the rolling piston 219. The drivingshaft 213 includes an eccentric member 215 provided to a part coupledwith the rolling piston 219 to be eccentric with respect to the centerof the driving shaft 213.

As the driving shaft 213 rotates, a radial load in a radial directionand a thrust load in a rotational direction of the shaft 213 aregenerated.

The cylinder 217 is formed in a lower part of the housing 211 so that acompressed refrigerant can flow in and out. The cylinder 217communicates with a valve (not shown), etc. so that the refrigerant maybe sucked from and discharged into the cylinder 217. The rolling piston219 is eccentrically disposed inside the cylinder 217.

The rolling piston 219 is coupled with the eccentric member 215 of thedriving shaft 213 to rotate together with the eccentric member 215 asthe driving shaft 213 rotates.

A vane (not shown) is coupled to the cylinder 217 to move into and outof the cylinder 217 to reciprocate in a radial direction of the drivingshaft 213. An end part of the vane contacts an outer surface of therolling piston 219 to create a compression chamber and a suction chamberwithin the cylinder 217.

The brushless direct current motor 230 includes the rotor 231, a stator240 and a load prevention part 250.

The rotor 231 includes a permanent magnet 233 to generate a magneticfield. The rotor 231 is coupled with the driving shaft 213 to rotate.

A plurality of coils 243 are wound around one or more iron cores 241 andwhen supplied with power, generate an electric field to generate torqueby interaction with a magnetic field generated by the permanent magnet233 of the rotor 231. The load prevention part 250 is coupled to a lowerend part of the stator 240.

The coils 243 are arranged in a plurality of phases U, V and W, and arewound around one or more iron cores 241. An insulating member (notshown) is disposed between each coil 243 and the associated iron core241. Each coil 243 is electrically connected with a stationary contactpoint 251 a of a casing 251 of the load prevention part 250. The coils243 are exemplarily arranged in three phases U, V and W. Alternatively,the coils 243 may be arranged in phases of six, twelve, etc. The coils243 may further include a coil for grounding.

The plurality of phases of the coils 243 are referred to as U1, U2, V1,V2, W1 and W2 for discriminating reciprocal connections as illustratedin the figures. Hereinafter, for a convenient description, U1 and U2 maybe referred to U, V1 and V2 may be referred to V, and W1 and W2 may bereferred to W.

In this example, load prevention part 250 includes the casing 251, amoveable member 253, a transformable member 255, an elastic member 257,a movement sensor 259, and a rotation prevention member 261.

The casing 251 is connected to the stator 240, and is coupled with eachphase U, V and W of the coils 243. The casing 251 preferably is made ofa nonconductive material. The casing 251 may have various shapes such asa cylindrical shape, a rectangular tube shape, etc. formed about aninner space. The casing 251 respectively supports the stationary contactpoint 251 a in a central area thereof, and the transformable member 255in a lower area thereof. The movement sensor 259 may be disposed to anupper part of the casing 251 as desired. The casing 251 may be supportedby an insulating member, such as plastic, to insulate the iron cores 241from the coils 243.

The moveable member 253 is coupled to an inner part of the casing 251 toconnect pairs of coils (of coils 243), each pair associated with one ofthe plurality of phases U, V and W. Specifically, the moveable member253 includes moveable signal lines 253 a each having movable contactpoints provided at opposite ends thereof to contact the stationarycontact points 251 a of a coil pair of a corresponding phase. Themoveable member 253 has a circular plate shape, and the moveable signallines 253 a are layered so that the moveable signal lines 253 a crossingeach other are not electrically connected with each other.

The moveable member 253 moves according to a temperature variationbetween a connected position in contact and electrically connected withthe stationary contact point 251 a of the casing 251, and a disconnectedposition, separated from the coils 243, out of contact and electricallydisconnected with the stationary contact points 251 a. The moveablemember 253 may include rotation prevention member 261 to preventrotation with respect to a moving axis of the moveable member 253 whenthe moveable member 253 moves up and down between the connected positionand the disconnected position. In this example, the absence of currentflowing in the coils 243 may be sensed by a terminal voltage sensor 283to determine that the moveable member 253 has moved to separate thestationary contact points 251 a from the moveable contact points 253 bto determine that the plurality of phases U, V and W of the coils 243are not electrically connected.

The transformable member 255 is supported by the casing 251 and istransformed according to a temperature variation to move the moveablemember 253 between the connected position and the disconnected positionaccording to the transformation. The transformable member 255 includesmaterial such as a bimetal transformed according to the temperaturevariation. The transformable member 255 includes a flat part 255 apositioned to surface-contact a central area surface of the moveablemember 253 so that the moveable member 253 can stably move withouttilting. Accordingly, the stationary contact point 251 a can stablycontact and separate from the moveable contact point 253 b.

The transformable member 255 has a thin circular plate shape.Alternatively, the transformable member 255 may have various shapes suchas a long rod shape, etc. as necessary. That is, the transformablemember 255 may have a shape, a thickness, a size, etc. so that thestationary contact point 251 a and the moveable contact point 253 b areseparated from each other to electrically disconnect each coil pair ofphases U, V and W.

Accordingly, the transformable member 255 may be easily transformedaccording to a temperature variation of an inner part of the casing 251or the stator 240. Since the transformation of the transformable member255 reflects the temperature variation of an inside part of thecompressor 210 at the most adjacent position, reliability of thecompressor 210 is improved.

Here, the control part may discontinue power supply applied to thestator 240 when the transformable member 255 moves from the connectedposition to the disconnected position.

The elastic member 257 is interposed between the casing 251 and themoveable member 253 to elastically press the moveable member 253 towardthe transformable member 255. The elastic member 257 has an elasticforce pressing the moveable member 253 toward the transformable member255 so that the moveable contact points 253 b contact the stationarycontact points 251 a to connect the coil pairs (of coils 243) when thetransformable member 255 has not been transformed due to a dangeroustemperature.

Accordingly, the stationary contact point 251 a can be kept to be stablycontacted with the moveable contact point 253 b by the press of theelastic member 257.

The movement sensor 259 is coupled to the casing 251 to sense a movementof the moveable member 253. That is, the movement sensor 259 senseswhether the moveable member 253 moves between the connected position andthe disconnected position according to the temperature variation of thetransformation member 255. The movement sensor 259 may selectivelyemploy various known sensors such as a photo sensor, etc., being capableof measuring the displacement of the moveable member 253. A resultsensed by the movement sensor 259 is transmitted to the control part270. Accordingly, the control part 270 can control power supplied to thestator 240 based on a received signal, e.g., from the movement sensor259, indicating that the moveable member 253 is electricallydisconnected.

Accordingly, the movement of the moveable member 253 can be stablysensed.

The rotation prevention member 261 prevents the moveable member 253 fromrotating about the moving axis when the moveable member 253 movesbetween the connected position and the disconnected position. Asillustrated in FIGS. 5A and 5B, the rotation prevention member 261includes a rotation prevention slot 261 a formed within the moveablemember 253, and a rotation prevention protrusion 261 b protruding froman inners wall of the casing 251 and engaged with the rotationprevention slot 261 a to guide the moveable member 253. Alternatively,the rotation prevention slot 261 a may be provided on the inner wall ofthe casing 251, and the rotation prevention protrusion 261 b may beprovided on the moveable member 253.

Accordingly, the moveable member 253 can stably move between theconnected position and the disconnected position without rotating.

Accordingly, even when the compressor 210 operates in a poorenvironment, the brushless direct current motor 230 is protected despiteany temperature variation of the interior of the compressor 210. Also,the load prevention part 250 may have a simple configuration.

The control part 270 may control the brushless direct current motor 230not to operate if the transformable member 255 is transformed so thatthe moveable member 253 is moved from the coils 243 and electricallydisconnected therewith. That is, if the moveable member 253 ispositioned at the disconnected position, the control part 270 may notsupply power to the stator 240, and if the moveable member 253 ispositioned at the connected position, the control part 270 may supplythe power to the stator 240. The control part 270 may include analgorithm regulating the power supply depending on the movement of themoveable member 253.

In this example, control part 270 generates a pulse width modulated(PWM) control signal based on results of a current sensor 281, a phasesensor 285 and the terminal voltage sensor 283, and transmits the PWMcontrol signal to the inverter part 293.

The sensor part 280 includes the phase sensor 285 which may be a hallsensor, a resolver element, an encoder, and/or other known sensors inthe art sensing the position of the rotor 231 of the brushless directcurrent motor 230. The phase sensor 285 may include a senseless typephase sensor to indirectly sense the position of the rotor 231. Thesensor part 280 may further include the terminal voltage sensor 283 tosense the amount of current applied to the stator 240.

Accordingly, the brushless direct current motor 230 can stably operate,and reliability of the operation can be improved.

The rectifier 291 rectifies an alternating current power to supply adirect current power, and includes a rectifier (not shown), and asmoothing condenser (not shown).

The inverter part 293 inverts the direct current power supplied from therectifier 291 into a pulse type alternating current power of threephases U, V and W having a variable frequency, and supplies thealternating current power to the brushless direct current motor 230. Inthis example, inverter part 293 includes a known switching circuit withsix switching elements Q1 to Q6, and six diodes.

The current sensor 281 senses current rectified by the rectifier 291.

Accordingly, the control part 270 can generate the PWM control signal ina signal generating unit 271 based on the results of the sensor part280, the movement sensor 259, etc., and transmit the PWM control signalto the inverter part 293. Here, the control part 270 may control powersupplied to the stator 240 in consideration of the position of themoveable member 253 according to the temperature variation of the innerpart of the compressor 210.

Here, the control part 270 may be part of the outdoor control part 125if desired.

Hereinafter, an operating process of the compressor 210 of the airconditioner 100 according to an exemplary embodiment will be describedby referring to FIGS. 1, 2, 3 and 6A to 6C.

If power is supplied to the air conditioner 100, the power is convertedby the rectifier 291 and the inverter part 293 to be supplied to thestator 240 of the compressor 210. Accordingly, the rotor 231 and thedriving shaft 213 coupled to the rotor 231 rotate by interaction of thestator 240 and the rotor 231. As the eccentric member 215 provided tothe lower part of the driving shaft 213 rotates, the rolling piston 219coupled to an outer surface of the eccentric member 215 rotates.Accordingly, the suction chamber and the compression chamber arepartitioned by means of the vane coupled to the cylinder 217 to becontacted with the rolling piston 219, and a process of sucking,compressing and discharging of the refrigerant is repeated by rotationof the rolling piston 219.

That is, if a user selects a heating mode of the air conditioner 100,the compressor 210 compresses a refrigerant. The compressed refrigerantis supplied to the indoor heat exchanger 111, and heat is exchangedbetween the indoor air and the indoor heat exchanger 111 using theindoor fan 113 so that heated air can be transferred into a room,thereby heating the room. The refrigerant passing through the indoorheat exchanger 111 is supplied to the outdoor heat exchanger 121.

If the user selects a cooling mode of the air conditioner 100, thecompressor 210 compresses the refrigerant. The compressed refrigerant issupplied to the outdoor heat exchanger 121 and evaporated in the indoorheat exchanger 111, and heat is exchanged between the indoor air and theindoor heat exchanger 111 using the indoor fan 113 so that a cooled aircan blow into the room, thereby cooling the room. The refrigerantpassing through the indoor unit 110 is returned to the compressor 210,and the outdoor heat exchanger 121.

In this process, the control part 270 controls power supply to thebrushless direct current motor 230 as described above.

Hereinafter, transformation of the transformable member 255 due to adangerous temperature such as an abnormal high temperature of the innerpart of the compressor 210 during a normal operating process will bedescribed.

At first, as illustrated in FIG. 6A, if an abnormal temperature isgenerated inside the compressor 210, the transformable member 255 isexpanded so that flat part 255 a overcomes a pressing force of theelastic member 257 to upwardly lift the moveable member 253. Thus, theelastic member 257 contracts. Accordingly, the stationary contact point251 a and the moveable contact point 253 b are separated from each otherto electrically disconnect each of the coil pairs (of coils 243)associated with phases U, V and W.

That is, as illustrated in FIGS. 6B and 6C, the coil pairs 243 arechanged from an electrical connecting state in which each of the coilpairs associated with phases U, V and W are electrically connected (asillustrated in FIG. 6B) to an electrical disconnecting state in whicheach of coil pairs associated with the phases U, V and W areelectrically disconnected (as illustrated in FIG. 6C).

The disconnection of the coil pairs may be sensed by the movement sensor259 or the terminal voltage sensor 283, and the sensed result istransmitted to the control part 270. Accordingly, power supplied to thebrushless direct current motor 230 may be cut off based on the sensedresult. Preferably, an algorithm is used to determine whether to cut offpower supplied to the brushless direct current motor 230.

Then, if the temperature of the inner part of the compressor 210 becomesnormal, the return of the movable member 253 to the connected positionis sensed by the movement sensor 259 or the terminal voltage sensor 283,and the control part 270 responds to supply the power to the brushlessdirect current motor 230.

The air conditioner according to the present general inventive conceptmay be applied to an air conditioner of various known types and is notlimited to an indoor unit, an outdoor unit, a heat pump, etc.

As described above, the present general inventive concept provides abrushless direct current motor, a compressor and an air conditionerhaving the same reliably operable within various environments.

Also, the present general inventive concept provides a brushless directcurrent motor, a compressor and an air conditioner having the same witha simple configuration more accurately responsive to the temperature ofthe motor of the environment within which it is used, thereby improvingreliability.

Although a few exemplary embodiments of the present general inventiveconcept have been illustrated and described, it will be appreciated bythose skilled in the art that changes may be made in these exemplaryembodiments without departing from the principles and spirit of thegeneral inventive concept, the scope of which is defined in the appendedclaims and their equivalents. As used in this disclosure, the term“preferably” is non-exclusive and means “preferably, but not limitedto.” Terms in the claims should be given their broadest interpretationconsistent with the general inventive concept as set forth in thisdescription. For example, the terms “coupled” and “connect” (andderivations thereof) are used to connote both direct and indirectconnections/couplings. As another example, “having” and “including”,derivatives thereof and similar transition terms or phrases are usedsynonymously with “comprising” (i.e., all are considered “open ended”terms)—only the phrases “consisting of” and “consisting essentially of”should be considered as “close ended”. Claims are not intended to beinterpreted under 112 sixth paragraph unless the phrase “means for” andan associated function appear in a claim and the claim fails to recitesufficient structure to perform such function.

1. A brushless direct current motor, comprising: a rotor which comprisesa permanent magnet; a stator which comprises plurality of coils arrangedin phases which form an electrical field to generate a torque byinteraction with a magnetic field which is generated by the permanentmagnet; and a load prevention part which is disposed inside the statorto electrically connect and disconnect the coils according to atemperature variation.
 2. The brushless direct current motor accordingto claim 1, wherein the plurality of coils are arranged in groups, eachgroup of coils being associated with a corresponding phase, and coils ofeach group being connected to each other with electrical connections,and wherein the load prevention part is disposed in an area in which theelectrical connections connecting coils of each group electricallyoverlap with one another.
 3. The brushless direct current motoraccording to claim 1, wherein the plurality of coils are arranged ingroups, each group of coils being associated with a corresponding phase,and wherein the load prevention part comprises: a casing which iscoupled to the stator, a moveable member which is disposed within thecasing to connect coils of each group of coils, and a transformablemember which is coupled to the casing to move between a connectedposition in which the moveable member is connected with the coils, and adisconnected position in which the moveable member is disconnected fromthe coils.
 4. The brushless direct current motor according to claim 3,wherein the transformable member comprises a bimetal.
 5. The brushlessdirect current motor according to claim 3, wherein the load preventionpart further comprises an elastic member which elastically presses themoveable member toward the transformable member.
 6. A compressor,comprising: a brushless direct current motor which comprises a rotorwhich comprises a permanent magnet, a stator which comprises a pluralityof coils, associated with corresponding phases, which form an electricalfield to generate a torque by interaction with a magnetic field which isgenerated by the permanent magnet, and a load prevention part which isdisposed inside the stator to electrically connect and disconnect thecoil of the plurality of phases according to a temperature variation;and a cylinder which compresses a substance by rotation of the brushlessdirect current motor.
 7. The compressor according to claim 6, whereinthe plurality of coils are arranged in groups, each group of coils beingassociated with a corresponding phase, and coils of each group beingconnected to each other with electrical connections, and wherein theload prevention part is disposed in an area in which the electricalconnections connecting coils of each group electrically overlap with oneanother.
 8. The compressor according to claim 6, wherein the pluralityof coils are arranged in groups, each group of coils being associatedwith a corresponding phase, and wherein the load prevention partcomprises: a casing which is coupled to the stator, a moveable memberwhich is disposed at an inner side of the casing to connect coils ofeach group of coils, and a transformable member which is coupled to thecasing to be transformed according to a temperature variation to movethe moveable member.
 9. The compressor according to claim 8, wherein theload prevention part further comprises: an elastic member whichelastically presses the moveable member toward the transformable member.10. The compressor according to claim 8, further comprising: a controlpart which controls the brushless direct current motor not to operate ifthe transformable member is transformed to separate the moveable memberfrom the coil.
 11. An air conditioner, comprising: a compressor tocompress a refrigerant, and comprising: a brushless direct current motorwhich comprises a rotor which comprises a permanent magnet, a statorwhich comprises a plurality of coils, associated with correspondingphases, which form an electrical field to generate a torque byinteraction with a magnetic field which is generated by the permanentmagnet, and a load prevention part which is disposed inside the statorto electrically connect and disconnect the coil of the plurality ofphases according to a temperature variation; and a cylinder whichcompresses a substance by rotation of the brushless direct currentmotor; a heat exchanger to evaporate the refrigerant which is compressedby the compressor; and a fan to form a flow to allow heat exchange withthe heat exchanger.
 12. The air conditioner according to claim 11,wherein the plurality of coils are arranged in groups, each group ofcoils being associated with a corresponding phase, and coils of eachgroup being connected to each other with electrical connections, andwherein the load prevention part is disposed in an area in which theelectrical connections connecting coils of each group electricallyoverlap with one another.
 13. The air conditioner of claim 11, whereinthe plurality of coils are arranged in groups, each group of coils beingassociated with a corresponding phase, and wherein the load preventionpart comprises a casing which is coupled to the stator, a moveablemember which is disposed to an inner side of the casing to connect coilsof each group of coils, and a transformable member which is coupled tothe casing to be transformed according to a temperature variation tomove the moveable member.
 14. The air conditioner according to claim 11,wherein the load prevention part further comprises an elastic memberwhich elastically presses the moveable member toward the transformablemember.
 15. The air conditioner according to claim 10, furthercomprising: a control part which controls the brushless direct currentmotor not to operate if the transformable member is transformed toseparate the moveable member from the coil.